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Space Telescope Users Committee
November 1997

The Space Telescope Users Committee met in open session on 24-25 November 1997, in the Board Room of the Space Telescope Science Institute. Committee members in attendence were: W. van Breugel, J. Clarke, R. Fosbury, L. Kay, P. McCarthy, R. Schulte-Ladbeck, S. Terebey, R. Thompson, F. Walter (Chair), and B. Woodgate. Absent were J. Bally and M. Franx.

Minutes of the meeting are reported elsewhere.

This meeting featured no large crises, and hence our report has little coherence, but is rather a shopping list of concerns. Some of these are new, while others are carried over from previous meetings.

The role of the STUC is not to be critical, but rather to point out concerns which affect the users of the HST, its archival database, and its services. Although the meetings, and this report, tend to harp on what is wrong, or what could be better, we realize the sheer complexity of the HST and the efforts undertaken by the HST project and the STSCI to keep everything functioning smoothly. We applaud everyone involved in this project for all the hard work they have put in, from those in the trenches, who are overworked and underappreciated, to those at the top who must bear the brunt of the criticisms. It continues to be astonishing how well such a complex operation as the HST functions.

STScI Manpower

The total investment in HST and its instrument suite is huge. The scientific value of the hardware is directly dependent on the quality and quantity of the instrument science effort which can be devoted to understanding, calibrating and enabling the operation of the many modes of these instruments. Given the complexity of operation of NICMOS and STIS, the STUC is concerned that insufficient resources may be available to fully exploit the capabilities of these instruments. It is understood that the commissioning of all the capabilities cannot take place immediately and it is appreciated that the quality of work and the dedication of the instrument scientists and supporting personnel is very high. It is apparent, however, that the number of highly skilled people working on STIS and, particularly, NICMOS is so small that the characterisation of the instruments is slower than desirable. STUC urges the STScI to make a critical appraisal of the balance of its resources devoted to instrument science relative to other areas in order to address these concerns.

Southern Deep Field

The STUC concurs with the plans for the southern deep field, and anticipates that it will prove as scientifically exciting as did the Hubble Deep Field.

Proposal review / TAC comments

The STUC appreciates the large effort by the STScI to conduct a cycle 7-delta review of proposals for NICMOS on a very short timescale. The STUC acknowledges that the special circumstances may have required a more austere review process to decrease the workload on the STScI staff in dealing with proposal evaluation and response to users in a timely manner. The STUC is concerned, based on feedback from the user community to STUC members, that the adopted philosophy for the cycle 7-delta review process of

  1. minimizing feedback to users on proposal evaluation by using user "comment tables",
  2. allowing TAC panels to provide only advisory proposal rankings to the super-TAC, and
  3. prohibiting TAC-panels to adjust proposal requests when deemed appropriate,is not in the best general interest of users. The STUC therefore urges the STScI for future HST proposal cycles to let users (TAC-panels) be in more control of the proposal evaluation, and provide more useful feedback in the form of written comments to users afterwards.

Advanced Camera for Surveys

The STUC recommends that the HST Project support the efforts of the ACS Science Team to obtain an additional procurement of 2k x 4k CCDs, with the goal of acquiring high quality CCDs for the Advanced Camera. Because the ACS Science Team is presently exploring alternative ways to acquire high performance CCDs, we think it is imprudent to specify in detail how they should proceed. If the ACS team presents a convincing plan that balances cost against schedule, performance, and risk, we recommend that the project support the plan.


The STUC understands the difficulties faced by observers with deferred cycle 7 programs. The STUC wholeheartedly supports the efforts of the STScI to reduce the backlog of uncompleted cycle 5 and cycle 6 observations. We concur with the scheduling prioritization currently implemented.

Planetary Working Group

Knox Long observed that the Planetary Working Group (PWG) was completing work on the items that had earlier been raised by the STUC, and recommended that the group now be disbanded. Indeed, progress has been made on all fronts, and many tasks have been completed while in some areas the work is planned to be completed within the next few months. We applaud the personnel at STScI and on the instrument teams for their hard work and responsiveness on these issues. The STUC agrees to disbanding the committee subject to the competion of all action items, and we hope that this can happen at the next STUC meeting in May 1998 following a presentation and discussion among the committee members. At the same time, in the past there have been recurring needs for such a group to address new issues, which might again arise at some time in the future. The specific items not yet completed are 1) distributing planetary target "finding charts" to observers on a regular basis, 2) extension of track 51 segments to times longer than 33 minutes so that consecutive observations during the same visibility period can be related to each other in absolute pointing, and 3) any issues that arise from early observations with NICMOS and STIS.

One particular area to be watched will be the success rates of STIS and NICMOS observations of moving and planetary targets, for which statistics are now being accumulated. Specific questions for STIS and NICMOS observations will be 1) reasons for any failed observations, 2) accuracy of pointing and acquisitions, and 3) accuracy of post-observation pointing and ancillary information. In particular, it remains to be seen how accurately the observer can register the pointing with STIS spectra either by target acquisition or following imaging. In the case of moving targets, the pointing with respect to the center of a planet between consecutive exposures is often not maintained, for example if the start times of linear track segments are not exactly what was planned, so that an image does not necessarily show where the aperture was pointed in a following spectrum. We hope that this issue can be addressed and put to rest at the May STUC meeting.

Archival CP

The STUC notes that the length of cycle 7 is nearly 2 years. Because the archival proposal process is tied to the observing cycle, users of the archive will not have had a recent opportunity to propose for support for their research. As grants are usually awarded on an annual basis, this has caused financial hardships. The STUC urges that an archival proposal opportunity be offered as soon as possible.

This special archival oportunity would follow the precedent set for the NICMOS delta-CP. As the observing cycle returns to an annual cycle, a single call for proposals would cover both archival and observing opportunities.

We note with satisfaction that NASA and the STScI have agreed to a special archival proposal opportunity to address this issue.

Support for New Users

STScI does a thorough job providing documentation and support for users. However the system is very complex and time consuming to learn, and can be overwhelming for new users. New users have special needs to get them onboard quickly -- overviews, tips, and cookbook documentation. These need not be time consuming tasks for Institute Staff to be worthwhile.

These recommendations mainly concern a particular type of new user: those unaffiliated with institutions, or those at small institutions with limited institutional support. Efficient use of the phase II proposal preparation tools requires either a SUN workstation or access to a fast internet connection.

The kind of help which would prove would most useful includes:

Pre-phase II travel support to the STScI to learn how to use RPS2 and to generate the Phase II proposal. A user without a SUN workstation or a quality internet connection is at a particular disadvantage, and there is generally insufficient time between announcement of the Phase I results and the Phase II deadline to obtain funding to purchase and install appropriate hardware.

Special assistance provided by STScI staff to new users. This assistance would entail a greater greater level of effort (per GO) than is possible for the program coordinators or contact scientists.

New users also benefit from training in how to use the data reduction software. Please continue to encourage new user visits, and provide the staff needed to support those visits.

Software Support

The STUC appreciates the difficult job that the software support personnel have in attempting to keep STSDAS current, between the new instruments, upgrades of IRAF, and the multitude of platforms observers wish to use. Some of the recent difficulties in obtaining up-to-date versions of STSDAS are due to inevitable delays in porting IRAF 2.11 from SUNs to other platforms (over which the STScI has no control). The STUC supports the decision to port the pipeline software to OpenIRAF (coded in C). The STUC admonishes the user community not to expect miracles.

STUC Membership

The STUC is comprised of 12 members, each of whom serves a 3 year term beginning with the Spring meeting. In principle, 4 new members are selected each year. The carryover of 8 members provides for a strong continuity to the committee. Due to three resignations, there were 7 new members selected in 1996. When these members rotate off in November 1998, there will be left only 5 members with experience. The STUC recommends that the two members rotating off this year be replaced with 4 members, and the 7 rotating off in 1998 be replaced with 5 members in 1999. The STUC will have 14 members for one year, and 7 returning members for 1999. The STUC recommends that, as policy, the PIs of newly installed instruments be voting members of the STUC for a normal 3 year term beginning near the time of instrumenmt installation. The PI of the ACS should join the STUC in May 2000. This ensures a voice for the GTOs, as well as the GOs. The STUC recommends that the PIs of all instruments selected for future flight be non-voting members of the STUC, and be encouraged to attend the full meetings.

The NICMOS Cryocooler

The committee remains less than enthusiastic about the proposed NICMOS cryocooler. As we stated in our May 1997 report, "Any decision to fly a cryogenic cooler for NICMOS should be made only after due considerations of all potential impacts on the spacecraft and the other instruments, and on the financial resources of the project. Funding for the cryogenic cooler must not be taken from UPN 459, and must not decrease the funding available for the year 2002 instrument."

The committee is also concerned that, even if the cryocooler is proven a viable concept, the scientific return from NICMOS in the era of large ground-based IR-optimized telescopes, adaptive optics technology, and improved detector technology may not be cost-effective. We recommend that this matter be investigated further.


The STUC was informed that the HST project is considering building a spare camera (WF3) from parts available from WFPC1 and utilizing spare ACS detectors. The motivation is to provide backup imaging capability for the extended HST mission through 2010. The STUC is concerned about both how the decision to do this was arrived at, and how the new instrument will be funded.

There are concerns that this decision compromises the peer-review process. If the project sees a need to construct a facility instrument, it should convene an open panel to recommend an instrument design.

The STUC is concerned about the source of funding for this instrument. We strongly recommend against use of UPN459 funds, especially if this reduces the amount of funding available to the GOs.

This report submitted by Frederick M. Walter on behalf of the Space Telescope Users Committee February 1998